Mechanical joining apparatus and mechanical joining method

Abstract

Provided is a mechanical joining apparatus enabling reduction of breakage of the area around a rivet of a joint obtained by riveting, the apparatus comprising a punch and die, blank holder, first power device, second power device and cooling device, wherein the first power device is configured to start supply of current through the holder and die so as to raise the temperature of the sheets before the punch drives in the rivet, the second power device is configured to start supply of current through the punch and die so as to supply current through and heat treat the rivet after the punch drives in the rivet, and the cooling device is connected to the punch and is configured to cool the rivet after the rivet is heat treated.

The invention claimed is: 
     
       1. A mechanical joining apparatus using a punch to drive a rivet into a plurality of metal sheets, the mechanical joining apparatus comprising
 a punch and die, 
 a blank holder, 
 a first power device, 
 a second power device, and 
 a cooling device, wherein 
 the punch and die are arranged facing each other so as to enable the punch and die to sandwich a superposed plurality of metal sheets between the punch and die, 
 the blank holder is a tubular member inside of which the punch can be inserted and is configured by an electrode material able to push against the plurality of metal sheets and able to electrically heat the plurality of metal sheets by one end of the blank holder being made to contact a punch side metal sheet of the plurality of metal sheets, 
 the punch is comprised of a material able to drive in a rivet and able to electrically heat the rivet, 
 the die is comprised of an electrode material able to support the plurality of metal sheets and able to electrically heat the rivet, 
 the first power device is configured to start supply of current through the blank holder and the die so as to raise the temperature of the plurality of metal sheets before the punch drives in the rivet, 
 the second power device is configured to start supply of current through the punch and the die so as to supply current through and heat treat the rivet after the punch drives in the rivet, and 
 the cooling device is connected to the punch and is configured to cool the rivet after the rivet is heat treated, 
 wherein in the die, at least a part facing the rivet across the plurality of metal sheets is made of tool steel and a part at the outer circumference of the tool steel is made of copper or copper alloy. 
 
     
     
       2. The mechanical joining apparatus according to  claim 1 , wherein the cooling device is configured to cool the rivet in a period from the start of the driving in of the rivet to the end of the driving in of the rivet. 
     
     
       3. A mechanical joining method using a punch to drive a rivet into a plurality of metal sheets, the mechanical joining method comprising
 preparing a plurality of metal sheets, 
 placing the plurality of metal sheets stacked between a punch and die arranged facing each other, 
 pushing one end of a blank holder comprised of a tubular member inside of which the punch can be inserted against a punch side metal sheet of the plurality of metal sheets, 
 using the punch to drive a rivet into the plurality of metal sheets held by the blank holder, 
 electrically heating the plurality of metal sheets through the blank holder and the die so as to raise the temperature of the plurality of metal sheets before driving in the rivet, and 
 electrically heating the rivet through the punch and the die after using the punch to drive in the rivet, then cooling the rivet, 
 wherein the method further comprising cooling the rivet through the punch in a period from the start of the driving in of the rivet until the end of the driving in of the rivet. 
 
     
     
       4. A mechanical joining method using a punch to drive a rivet into a plurality of metal sheets, the mechanical joining method comprising
 preparing a plurality of metal sheets, 
 placing the plurality of metal sheets stacked between a punch and die arranged facing each other, 
 pushing one end of a blank holder comprised of a tubular member inside of which the punch can be inserted against a punch side metal sheet of the plurality of metal sheets, 
 using the punch to drive a rivet into the plurality of metal sheets held by the blank holder, 
 electrically heating the plurality of metal sheets through the blank holder and the die so as to raise the temperature of the plurality of metal sheets before driving in the rivet, and 
 electrically heating the rivet through the punch and the die after using the punch to drive in the rivet, then cooling the rivet, 
 wherein in the die, at least a part facing the rivet across the plurality of metal sheets is made of tool steel and a part at the outer circumferences of the tool steel is made of copper or copper alloy. 
 
     
     
       5. The mechanical joining method according to  claim 3 , wherein in the die, at least a part facing the rivet across the plurality of metal sheets is made of tool steel and a part at the outer circumferences of the tool steel is made of copper or copper alloy.